group size measuring

wolf300H&H

wolf300H&H

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hey fellow target slayers,just been having a interesting chat with another 204 fan and he told me you measure the group with the outside of the bullet then subtract the calibre size .is this true? i thought you measured the center to center of the furthest holes! help me out
 
If I read you correctly, the two methods will give you basically the same answers (measuring the outside of the hole will add 1/2 of the diameter of the bullet to each hole ...... using two holes will add the diameter/caliber of the bullet to the actual distance).

Nevertheless, I believe that the more accurate way is to estimate the centers of the furthest two holes and measure this distance. In serious competitive shooting (some years ago), a device was used to estimate the center of the hole.

Duke1
 
Group size is measured center to center of the furthest shots. Period.

If you do not have a tool made to do this, this measurement can be made by measuring outside to outside of the furthest shots and subtracting the diameter of a single hole made in that target paper by that particular rifle.... not always the caliber of the bullet. Bullets cut different size holes depending on the bullet and the paper and the humidity.
 
I read somewhere if you spray the papar with starch and let it dry overnight the holes a nicer, cleaner, may be easy to measure
 
I was the member who measures this way.. I measure outside to outside and take the diameter away..easier than center to center for my purposes. Any problems with that? Both these groups are under.. .2" measured both ways
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It simply depends on what diameter you are taking away... it is not always bullet diameter...

the diameter of a single hole made in that target paper by that particular rifle.... not always the caliber of the bullet. Bullets cut different size holes depending on the bullet and the paper and the humidity.

...and it does not look like your caliper is on the farthest apart holes... you have to measure them all and I draw a line through the final longest measurement showing which holes...

excellent groups by the way...
 
guntech said:
It simply depends on what diameter you are taking away... it is not always bullet diameter...

the diameter of a single hole made in that target paper by that particular rifle.... not always the caliber of the bullet. Bullets cut different size holes depending on the bullet and the paper and the humidity.

...and it does not look like your caliper is on the farthest apart holes... you have to measure them all and I draw a line through the final longest measurement showing which holes...

excellent groups by the way...
Click to expand...

Yes should have been more clear on the diameter of a bullet hole..
 
Fire a 3 shot group, subtract one as a warming and call another a "called flyer". Half the diameter of your bullets and then post your size on CGN as your best group with a factory rifle and factory loads. :p
 
measurement

the center to center measuring is fine , but if the bullet holes all form a ragged hole or a bit bigger hole than the calibre then i think thats a good way to measure the group(subtracting the calibre).cause i have a .298 group(once) that convinced me to stick with that load and its basically an enlarged 204 hole, so could i say that the group is .098?or do i say .298 edge to edge?
 
fralic76 said:
Google a program called "On Target", all you need is a picture of the target or you can scan in through the program.
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Thanks! http://www.6mmbr.com/ontargetsoftware.html

Very interesting software (free) and relatively easy to use.

Instructions are included with it and will work with a printer equipped with scanning capabilities including the HP 2175, etc. Did a quick run on a simulated target (scanned) and came up with very good results. I did not try a photo of a target but presume it works just as well.

Duke1
 
wolf300H&H said:
hey fellow target slayers,just been having a interesting chat with another 204 fan and he told me you measure the group with the outside of the bullet then subtract the calibre size .is this true? i thought you measured the center to center of the furthest holes! help me out
Click to expand...

I measure center to center because if you do the subtraction thing, you'll get a false (smaller) measurement.

For example, when shooting a .308 caliber on paper, the actual hole size (while subjective) is/was approx .280". Measuring .280" holes outside to outside diameters already will give you a false (smaller) group, and then you compound this by subtracting .308" from the measurement.

At least that's how it was explained to me....

I guess this method is great when you're trying to sell a precision piece;)
 
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zupermann said:
I measure center to center because if you do the subtraction thing, you'll get a false (smaller) measurement.

For example, when shooting a .308 caliber on paper, the actual hole size (while subjective) is/was approx .280". Measuring .280" holes outside to outside diameters already will give you a false (smaller) group, and then you compound this by subtracting .308" from the measurement.

I guess this method is great when you're trying to sell a precision piece;)
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Yeah..okay..:confused:

we just said you subtract the hole diameter...not the caliber diameter.. how would you measure a one hole group then?? C to C of the hole?
 
noneck180 said:
oh boy...
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Yeah, some weird advice coming along here.

Measure the edge-to-edge of the grease ring (not the hole, it varies a lot, but the dark marking that appears to be - but is not - a light smear of grease) at the group's widest point. Take away the bullet diameter... and that's your centre-to-centre measurement, which is what you want.

If you have digital callipers and don't want to do the math, set the callipers to your bullet diameter (e.g., in your case .204) then zero it. Then measure edge-to-edge on the grease ring. That's your group size.

If something funky happens because the paper was more or less damp, doesn't matter - the grease ring is fairly reliable and good enough for what you need.

There are fancy tools to measure at competitions, but for what you're doing you don't need them.

For example:
attachment.php
 
If you're just shooting targets for fun, just make sure you measure the same way so you know if things are getting better or worse. And if you're really worried about fractions of an inch, well, find a longer range so the hole size becomes less important. :)

Steve
 
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